A wide variety of procedures and different types of equipment are available for use in recapping or retreading tires. One of the first steps in retreading a worn tire is to remove existing tread material from the tire carcass by buffing. Various procedures are available to apply one or more layers of uncured rubber or retreading material with appropriate bonding agents to the buffed tire carcass. The uncured rubber may also be stitched to the buffed carcass as required. For purposes of this patent application, the term "built tire" is used to refer to a buffed tire carcass or casing which has been built up with one or more layers of uncured rubber and other material as required by the retreading equipment and procedures being used to retread the worn tire.
In the past, heavy duty mechanical and/or hydraulic closing devices have often been used to install molds which form a new tread in retreading material on a prepared tire carcass or built tire. Tire distortion sometimes occurs as the tread molds are closed on the built tire. This problem is particularly common if the built tire is slightly larger in diameter than desired. In such cases, the prepared tire carcass will often buckle and can thus no longer be used. Damage to a built tire during mold installation represents a substantial loss of time and material spent preparing the built tire for mold installation.
One method of recapping or retreading tires is illustrated in U.S. Pat. No. 4,767,480 entitled Cold Recapping Method for Tires Utilizing Uncured Rubber and Sectioned Mold, issued Aug. 30, 1988 to Leon C. Goldstein. This patent describes apparatus and methods for retreading which uses a cold process. In this process, a flexible tread mold is stretched over the prepared tire carcass. Subsequently, an envelope is placed over the mold and built tire and the entire unit or assembly is placed in a chamber for curing of the rubber. U.S. Pat. No. 4,588,460 entitled Method and Apparatus for Recapping a Tire with a Flexible Segmented Mold, issued May 13, 1986 to Arthur W. McGee, et al. illustrates another method and apparatus for retreading a tire that includes a relatively flexible mold which is formed by a plurality of mold segments. U.S. Pat. Nos. 5,306,130, entitled Apparatus for Recapping a Tire and an Improved Curing Envelope for Use Therein, and 5,342,462, entitled Apparatus and Method for Retreading a Tire, show other types of tire retreading equipment and methods.
Pneumatic tires may also be recapped or retreaded by installing a continuous replacement tread on a prepared tire carcass. Both uncured and cured rubber compounds have previously been used to provide continuous replacement treads. Examples of equipment and procedures to install continuous replacement treads on a tire casing are shown in U.S. Pat. Nos. 3,976,532 entitled Tread Applying Machine, dated Aug. 24, 1976 and issued to C. K. Barefoot; 4,088,521 entitled Method of Retreading a Tire with an Endless Premolded Tread, dated May 9, 1978 and issued to P. H. Neal; 4,036,677 entitled Machine for Treating Worn Out Pneumatic Tires and for Applying a PreMolded Tread Ring, dated Jul. 19, 1977 and issued to Carlo Marangoni; and 4,957,574 entitled Tread Centering Method and Apparatus, dated Sep. 18, 1990 and issued to A. R. Clayton, et al.
Retreading procedures often require the use of a flexible envelope to seal around the tire casing, retread material and tread mold. The complete assembly, including the tire casing, retread material, tread mold and envelope, are placed in a high pressure, high temperature chamber in preparation for curing the components which comprise the completed tire assembly. This chamber is frequently referred to as an autoclave. Examples of a tire retreading envelope and high pressure, high temperature curing chamber are shown in U.S. Pat. No. 4,309,234 entitled Tire Retreading Envelope Seal, dated Jan. 5, 1982 and issued to P. L. Witherspoon. U.S. Pat. No. 4,767,480 also contains information on such envelopes for curing retreaded tires.
The above listed patents are incorporated by reference for all purposes within this application.